Guideline for a healthy information system v.2.0 (EN)

/STANDARD
Noticing unusual behaviour from a workstation or a server (impossible connection, significant activity, unusual activity, unauthorised open services, files created, modified or deleted without authorisation, multiple anti-virus warnings, etc.) may be a warning of a possible intrusion. 

A bad reaction in the event of a security incident can make the situation worse and prevent the problem from being dealt properly. The right reaction is to disconnect the device from the network, to stop the attack. However, you must keep it powered and not restart it, so as to not lose useful information for analysing the attack. You must then alert the management, as well as the information system security point of contact. 

He or she may get in contact with the security incident response service providers (PRIS) in order to carry out the necessary technical operations (physically copying the disk, analysing the memory, logs and possible malware, etc.) and determine if other elements of the information system have been compromised. This will also concern coming up with a response to provide, in order to remove possible malware and the access that the hacker may have and to change compromised passwords. Any incident must be recorded in a centralised register. Charges may also be pressed with the competent legal service.